Data Sheet
Current-Setting Resistor - R
REF
Full-scale output current of each D/A converter is deter-
mined by the value of the resistor connected between
R
REF
and GND. Nominal value of R
REF
is found from:
R
REF
= 9.1 (V
REF
/I
FS
)
where I
FS
is the full-scale (white) output current (in amps)
from the D/A converter (without sync). Sync is 0.4 * I
FS
.
D/A full-scale (white) current may also be calculated from:
I
FS
= V
FS
/R
L
Where V
FS
is the white voltage level and R
L
is the total
resistive load (Ω) on each D/A converter. V
FS
is the blank
to full-scale voltage.
A 0.1µF capacitor must be connected between the COMP
pin and V
DD
to stabilize internal bias circuitry and ensure
low-noise operation.
Voltage Reference Output/Input - V
REF
An internal voltage source of +1.235V is output on the
V
REF
pin. An external +1.235V reference may be applied
here which overrides the internal reference. Decoupling
V
REF
to GND with a 0.1µF ceramic capacitor is required.
CDK3402/CDK3403
8-bit, 100/150MSPS, Triple Video DACs
Power and Ground
Required power is a single +5.0V supply. To minimize power
supply induced noise, analog +5V should be connected
to V
DD
pins with 0.1µF and 0.01µF decoupling capacitors
placed adjacent to each V
DD
pin or pin pair.
The high slew-rate of digital data makes capacitive cou-
pling to the outputs of any D/A converter a potential
problem. Since the digital signals contain high-frequency
components of the CLK signal, as well as the video out-
put signal, the resulting data feedthrough often looks
like harmonic distortion or reduced signal-to-noise perfor-
mance. All ground pins should be connected to a common
solid ground plane for best performance.
Voltage Reference
All three D/A converters are supplied with a common
voltage reference. Internal bandgap voltage reference
voltage is +1.235V with a 3kΩ source resistance. An
external voltage reference may be connected to the V
REF
pin, overriding the internal voltage reference.
Rev 1B
©2008 CADEKA Microcircuits LLC
www.cadeka.com
7
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
